python写文件时出有关问题

python写文件时出问题
异常代码如下：
write a file error: [Errno 2] No such file or directory: 'C:\x0cile.txt'

Traceback (most recent call last):
  File "C:\Documents and Settings\USER\桌面\复件 test.py", line 84, in <module>
  test()
  File "C:\Documents and Settings\USER\桌面\复件 test.py", line 78, in test
  writefile(s)
  File "C:\Documents and Settings\USER\桌面\复件 test.py", line 59, in writefile
  f.write(str(string))
UnboundLocalError: local variable 'f' referenced before assignment

Python code

。。。。。。。。。。。               
 
def writefile(string):
    strfile="C:\file.txt"
    try:
        f = open(strfile,'a')
    except IOError,e:
        print "write a file error:",e

    f.write(str(string))
    f.close()



def test():
    fname = 'C:\ZLLKDoc.cpp'
    #raw_input('Enter filename: ')
    try:
        fobj = open(fname, 'r')
    except IOError, e:
        print "*** file open error:", e
    strFile=fobj.read()

    fobj.close()
    
    s = eraser(strFile)
    print s

实在不知道哪里错了，请大侠们帮忙看看，感激不尽

------解决方案--------------------
转义成'C:\x0cile.txt' 不能当文件名
strfile="C:\file.txt" 改r"C:\file.txt"或"C:\\file.txt"或"C:/file.txt"